This invention relates to the field of electronic displays, and, more particularly, field emission display ("FED") devices.
As technology for producing small, portable electronic devices progresses, so does the need for electronic displays which are small, provide good resolution, and consume small amounts of power in order to provide extended battery operation. Past displays have been constructed based upon cathode ray tube ("CRT") or liquid crystal display ("LCD") technology. However, neither of these technologies is perfectly suited to the demands of current electronic devices.
CRT's have excellent display characteristics, such as, color, brightness, contrast and resolution. However, they are also large, bulky and consume power at rates which are incompatible with extended battery operation of current portable computers.
LCD displays consume relatively little power and are small in size. However, by comparison with CRT technology, they provide poor contrast, and only limited ranges of viewing angles are possible. Further, color versions of LCDs also tend to consume power at a rate which is incompatible with extended battery operation.
As a result of the above described deficiencies of CRT and LCD technology, efforts are underway to develop new types of electronic displays for the latest electronic devices. One technology currently being developed is known as "field emission display technology." The basic construction of a field emission display, or ("FED") is shown in FIG. 1. As seen in the figure, a field emission display comprises a face plate 100 with a transparent conductor 102 formed thereon. Phosphor dots 112 are then formed on the transparent conductor 102. The face plate 100 of the FED is separated from a baseplate 114 by a spacer 104. The spacers serve to prevent the baseplate from being pushed into contact with the faceplate by atmospheric pressure when the space between the baseplate and the faceplate is evacuated. A plurality of emitters 106 are formed on the baseplate, which is often a semiconductor substrate. The emitters 106 are constructed by thin film processes common to the semiconductor industry. Millions of emitters 106 are formed on the baseplate 114 to provide a spatially uniform source of electrons.
Constructing the substrate, or baseplate, typically involves the use of a series of masks according to techniques commonly used in the semiconductor industry. However, it is desirable to form a substrate using as few masks as possible because each mask represents an additional cost which must be incurred. Moreover, an additional manufacturing step is required for each mask. These additional manufacturing steps also add to the cost of the finished product. For example, FIG. 1A shows a typical field emission display substrate 150 having emitters 156 formed thereon. Various masks are required for the formation of emitters 156. After the emitters are formed, an insulating layer 152 is deposited on the substrate 150. More masks are required to deposit and etch the insulating layer 152. Finally, in order to provide an electrical field for generating emissions, grid layer 154 is deposited on top of insulating layer 152. Again, masks must be used to deposit and etch grid layer 154 to finally obtain the device shown in FIG. 1A. Further, it is crucial that the grid layer be accurately disposed on the substrate to avoid contacting the emitter, which would cause a short and thus destroy the emitter , or intruding into the path of the electrons which travel between the emitter and the faceplate. Accordingly, there is a need in the art for a field emission display which overcomes the above mentioned problems.